1) Field of the Invention
The present invention relates to a magnetic recording/reproducing apparatus and a magnetic recording/reproducing method that reproduce data recorded in a perpendicular magnetic recording disk, and more particularly to a magnetic recording/reproducing apparatus and a magnetic recording/reproducing method in which error rates are stabilized.
2) Description of the Related Art
Conventionally, a longitudinal magnetic recording system that records magnetism parallel to a disk surface had been widely used for recording systems of magnetic recording disks. However, to meet a demand for densification of recording volume, a perpendicular magnetic recording system that records magnetism in the direction perpendicular to a disk surface has been commercialized lately, for example, as disclosed in Japanese Patent Application Laid-Open Publication No. 2004-213896.
Since a head detected a perpendicular component of a magnetic field on a disk surface when reading out data recorded on the disk, it was equivalent to differentiation when information recorded by the longitudinal magnetic recording system was read out. Moreover, in a head preamplifier that served as an amplification processing unit to amplify a reproduced waveform outputted from the head, a bias current or a voltage was applied to the head to extract a variation in magnetoresistance of the head, and high-pass filters were used at both ends of the head to eliminate potential difference.
Here, since the reproduced waveform of the head has a differentiation characteristic in the longitudinal magnetic recording system, there was little effect on the error rate with respect to data transfer rate when cut-off frequencies of the high-pass filters are moderately low against the reproduced waveform band.
However, in the perpendicular magnetic recording system, a magnetic field on a disk is reproduced straight by the head. Therefore, reproduced signals have a direct current (DC) component, and their transfer rates vary depending on positions in radial direction on the disk. Accordingly, the reproduced waveform from the head varies according to the relation between the cut-off frequency of the high-pass filter in the head preamplifier and the data transfer rate, which results in a problem that influence upon the error rate occurs due to complication of a decryption system and an equalization error.